The human body contains a wide variety of natural valves, such as, for example, heart valves, esophageal and stomach valves, intestinal valves, and valves within the lymphatic system. Natural valves may degenerate for a variety of reasons, such as disease, age, and the like. A malfunctioning valve fails to maintain the bodily fluid flow in a single direction with minimal pressure loss. An example of a malfunctioning valve is a heart valve that may be either stenotic, i.e., the leaflets of the valve do not open fully, or regurgitant, i.e., the leaflets of the valve do not close properly. It is desirable to restore valve function to regain the proper functioning of the organ with which the valve is associated. For example, proper valve function in the heart ensures that blood flow is maintained in a single direction through a valve with minimal pressure loss, so that blood circulation and pressure can be maintained. Similarly, proper esophageal valve function ensures that acidic gastric secretions do not irritate or permanently damage the esophageal lining.
Several percutaneous prosthetic valve systems have been described. One example described in Andersen, et. al. (U.S. Pat. No. 5,411,552) comprises an expandable stent and a collapsible valve which is mounted onto the stent prior to deployment. The collapsible valve may be a biological valve or it may be made of synthetic material. The Anderson prosthetic valve is delivered and deployed using a balloon catheter which balloon is used to expand the valve-stent prosthesis to its final size. See also, U.S. Pat. No. 6,168,614 (Andersen, et al.) entitled “Valve Prosthesis for Implantation in the Body” and U.S. Pat. No. 5,840,081 (Andersen, et al.) entitled “System and Method for Implanting Cardiac Valves.”
Spenser, et. al. (U.S. Pat. No. 6,893,460) describe another prosthetic valve device comprising a valve structure made of biological or synthetic material and a supporting structure, such as a stent. The Spenser prosthetic valve is a crimpable leafed-valve assembly consisting of a conduit having an inlet and an outlet, made of pliant material arranged to present collapsible walls at the outlet. The valve assembly is affixed to the support stent prior to deployment. The complete valve device is deployed at a target location within the body duct using a deploying means, such as a balloon catheter or a similar device.
Percutaneous implantation of prosthetic valves is safer, cheaper, and provides shorter patient recovery time than standard surgical procedures. However, current artificial percutaneous prosthetic valves have the disadvantage of being bulky, even when compressed for delivery. The problem with this bulkiness is that the delivery diameter of current valve devices and required diameter delivery systems combined with the anatomy through which the devices must be delivered can make delivery into the lumen problematic from the point of view of success rate, accuracy of deployment, and risk of complications. Specifically, delivery complications may arise due to the shape of the lumen, for example, the significant natural curve of the aortic arch and/or a tortuous iliac/femoral artery through which the catheter is introduced. Further, a larger diameter catheter tends to be less flexible than a smaller diameter catheter, especially when loaded with a bulky, inflexible device, and manipulating such a loaded catheter through a narrow vessel and in particular a curved vessel substantially raises the potential for damage to that vessel wall.
The delivery diameter of a prosthetic percutaneous valve is dependent in part on the way in which the valve is folded. There is a need in the art for a prosthetic valve device that may be folded in a manner that minimizes the diameter of the device for delivery, thereby minimizing complications and increasing the safety of the valve replacement procedure. A device that can be placed in the vessel without incurring further damage to the wall of the body lumen is highly desirable.